The reason I'd never vote for McCain is that he, well, "supports" may be too strong a word, but refuses to oppose waterboarding. I'm not a single-issue voter, but there are non-negotiable issues for me, and anyone who won't come out and say that "torture is what the bad guys do, and we're not bad guys, so we will neither torture, nor try to weasel around it by calling it 'enhanced interrogation' or whatever" won't get my vote.